Find all exact radian solutions within the interval [π7,15π7)\displaystyle {\left[\frac{\pi}{{7}},\frac{{{15}\pi}}{{7}}\right)}. Separate different solutions using a comma, if needed. Express each final solution as a fraction of lowest terms. 

 cos⁡(x−π7)=\displaystyle {\cos{{\left({x}-\frac{\pi}{{7}}\right)}}}=−12\displaystyle -\frac{{1}}{{2}}

 x=\displaystyle {x}=

 

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